THYROID GLAND Location The thyroid gland is the largest gland in the body, secretes thyroxine and triiodothyronine, which function in the regulation of energy metabolism In an adults it weighs between 25 and 30 grams Location The thyroid gland is located in the neck, just below the larynx anterior and lateral to trachea

Structure of thyroid gland Thyroid gland is a butterfly shaped gland 5cm long It has two lobes on either side of trachea. The two lobes are connected to each other by a narrow band of tissue called isthmus which is present anterior to the trachea Microscopically thyroid gland is made up of spherical sacs called thyroid follicles A thyroid follicle has a wall which surround a central lumen The wall of thyroid gland is made up of cuboidal epithelial cells which are called follicular cells The cells synthesize thyroid hormones and secrete them into lumen of the follicle where it is stored in form of colloid Between the follicles are epithelial cells called parafollicular cells that produce a hormone called calcitonin, or thyrocalcitonin.

Blood Supply to Thyroid Gland Thyroid gland is extensively vascularized. Receives about 80-120 ml/min blood Two set of paired arteries supplies the thyroid gland The superior thyroid artery – paired arteries arises from the external carotid artery supplies the upper pole The inferior thyroid arteries- paired arteries from the thryocervical trunk of subclavian artery Three paired veins collects blood from thyroid gland The superior thyroid vein - drains the upper pole to the internal jugular vein; The middle thyroid vein - drains from the lateral side of the gland to the internal jugular; The inferior thyroid veins - drain the lower pole to the brachiocephalic veins

Nerve Supply: Sympathetic nervous system. Function of the thyroid Gland: T3 , T4 & Calcitonin synthesis. Protein synthesis. Release of energy from carbohydrate. Sexual maturity. Calcitonin inhibit the mobilization of calcium from the bones also causes increase excretion of calcium from the kidneys and so lowers the calcium level in the blood.

ADRENAL GLAND Location The paired adrenal (suprarenal) glands lies superior to each kidney in the retroperitoneal space They are protected by a pad of fat and also has a connective tissue capsule

Structure Pyramid shaped Size is about 5 cm (2 in.) long, 3 cm (1.1 in.) wide, and 1 cm (0.4 in.) deep Has structurally and functionally two different regions The adrenal cortex which is located peripherally and comprise 80 – 90 % of gland The adrenal medulla which is small central portion

Adrenal cortex It is the outer portion of adrenal gland and has distinctive yellow colour because of stored fat Histologically it can be divided into three different regions The outer most zone is called zona glomerulosa in which cells are closely packed and arranged in spherical clusters and arched columns, secrete hormones called mineralocorticoids The second zone is called zona fasciculata, is the widest of the three zones and consists of cells arranged in long, straight columns. Mainly secret glucocorticoids The inner most zone is called zona reticularis which secrets androgens

Adrenal medulla The inner core of adrenal gland Has distinctive red colour because of extensive vascularization The adrenal medulla primarily consists of clusters of large, spherical cells called chromaffin cells These cells secrets epinephrine and norepinephrine They are innervated by preganglionic sympathetic axons

Blood Supply to Adrenal Gland Receives three vessels a branch from the inferior phrenic artery- superior supra-renal artery a direct branch from the aorta- middle supra renal artery a branch from the renal artery – inferior supra renal artery The venous drainage from right adrenal gland is different from left adrenal gland The right supra renal vein drains directly to inferior venacava while the left supra renal vein drains to the renal vein

Pituitary gland The pituitary gland is a pea-shaped structure that measures1–1.5 cm in diameter It lies in the hypophyseal fossa of the sella turcica of the sphenoid bone It is located on the inferior aspect of the brain in the region of the diencephalon and is attached to the brain by a structure called the pituitary stalk or infundibulum. Circle of willis surrounds the pituitary gland.

Structure Posterior pituitary Anterior pituitary Pituitary gland has two anatomically and functionally separate portions: the anterior pituitary the posterior pituitary. Anterior pituitary The anterior pituitary also called the adenohypophysis, accounts for about 75% of the total weight of the gland The anterior pituitary consists of two parts in an adult: The pars distalisis the larger portion The pars tuberalis forms a sheath around the infundibulum Posterior pituitary The posterior pituitary also called neurohypophysis, is the neural part of the pituitary gland. It consists of two parts: The lobus nervosa which is bulbur poriton in contact with the adenohypophysis The infundibulum ,funnel shaped stalk of tissue that connects the pituitary to the base of the hypothalamus.

Hormones of Pituitary Gland: 9 different hormones are produced by Pituitary gland. 7 hormones are produced by anterior pituitary. 2 by posterior pituitary. Posterior pituitary mainly stores hormones that are produced by hypothalamus.

Pituitary Hypothalamus Connection